A closed-loop theory of motor learning

The Independence of Recall and Recognition in Motor Learning

A basic tenet of both current closed-loop theories of motor learning (Adams, 1971; Schmidt, 1975) is that the generation of response specifications during learning is required for the development of recall memory. Two experiments were performed to test this tenet by attempting to demonstrate the development of recall memory in the absence of response specification production. The task in both experiments required blindfolded subjects to learn to produce a rapid, novel criterion movement on a linear positioning device. Control subjects in both experiments actively produced movements during learning with knowledge of results (KR) while experimental subjects in Experiment 1 experienced only the endpoint locations and in Experiment 2 were passively moved to the endpoint locations. Following initial KR trials, both experimental and control groups attempted to actively produce the criterion movement in the absence of KR. The results of both experiments support closed-loop theory that active practice is required to develop recall memory. There was some suggestion, however, that passive experience with sensory feedback may also aid recall memory development, contrary to the two closed-loop theories.

Recall. And Recognition Processes in Motor Memory

In linear movement tasks of 200 msec (Experiment 1 -ballistic movement) and 500 msec (Experiment 2 - nonballistic movement), motor recall strength was assessed by absolute, constant, and variable error; recognition strength was assessed by Z'-transformed actual-estimate correlations and absolute actual-estimate difference scores. Contrary to predictions, neither increased KR delay (45 vs. 5 sec) nor limited visual-auditory-tactile feedback caused decrements in recognition processes over KR-training or KR-withdrawal trial blocks for the 200-msec task. In the 500-msec task, the independent variables impaired recognition through training and transfer trials but impaired recall only in the training trials. Results generally did not support the hypothesized independence between recall and recognition processes. Several methodological issues related to recall, and recognition research were discussed.

Diving, Adaptation, and Fitts Law

To assess Welford's dual controlling factor interpretation of Fitts' law, 20 scuba divers performed a reciprocal tapping task. In an attempt to separate the two factors, the subjects were tested on land and underwater. This does not change the basic parameters of the task but does put the subjects under informational stress, in that underwater the movement is less ballistic in nature and should require the processing of more information (feedback) in each tap. On land, the contributions of movement amplitude and precision were approximately equal. However, the relative changes in contribution of these factors to movement time underwater suggests that these parameters do in fact represent separate controlling factors.

On The Structure of Motor Recognition Memory

Two experiments determined the influence of the range and number of auditory sensory consequences, associated with a rapid timing task, on the development of motor recognition. Experiment 1 observed no beneficial effect upon subsequent movement-transfer performance from experience with the criterion-movement-time sound compared to experience with either a narrow or a wide range of sounds that bracketed the criterion sound (not including the criterion); 60 sound trials prior to transfer did not produce better transfer than did six sounds. The second experiment examined transfer outside of the range of previous listening experience by having subjects transfer to one of two possible criterion movement times after having received either constant, or one of two types of variable, listening experience. Transfer performance was influenced by the amount of variability in listening experience. These results were seen as support for a schematic representation for motor recognition memory (Schmidt, 1975)

Bereitschaftspontential during the acquisition of a skilled motor task

Bereitschaftspontential (BP) research typically uses very simple, abrupt movements that require no learning and which change little over the duration of the experimental session. The present study investigated changes in the size and cortical distribution of the BP during the acquisition of a skilled motor task. Twelve subjects were employed. Electrodes at FZ, CZ, C3'' and C4'' were used to record the EEG with DC amplifiers. A series of 6 button presses in a specified pattern constituted the motor task. Subjects were instructed to press the series every 20 sec as quickly as possible, but with no errors. Significant response time, electrode and trial main effects, and electrode by trial interactions were found. The BP increased steadily at all electrodes as performance improved, i.e., as response time decreased. After the response reached asymptote the BP recorded at FZ and C4'' decreased, while the BP at CZ and C3'' remained relatively constant. Multivariate analyses of covariance showed a consistent relationship between the improvement in response times and the changes in the BP. This study demonstrates that the size and cortical distribution of the BP are systematically related to improved proficiency of a motor response with learning.

Attention to Visual Feedback in Motor Learning

Visual guidance and movement to a stop were used to train subjects to make a simple movement without experiencing error in practice. Movement to a stop led to test performance as accurate as that after training with KR, but visual guidance did not. If a continuous visual cue as well as a stop were present during practice, subjects also performed less accurately, although they did not need to attend to the visual cue. All types of training were better than no training at all. Results are discussed in terms of the role of visual feedback in the development and assessment of programs for movement.

Effects of relative frequency of knowledge of results on retention of a motor skill

The effects of relative frequency of knowledge of results on the retention of a motor skill was studied. Adams' theory (1971) contends that the perceptual trace of a criterion position gains on increment of strenth each time the feedback stimuli associated with the criterion position are experienced and that it is the strength of the perceptual trace that determines retention. Schmidt's theory (1975), however, suggests that the recognition schema is updated only on trials on which the feedback stimuli associated with the criterion position are experienced in conjunction with knowledge of results and that it is the precision of the recognition schema that determines retention. Two experiments were conducted. The results provided evidence contrary to Adams' theory. Schmidt's theory, however, was only partially supported.

Shifts in Attention Demands and Motor Program Utilization During Motor Learning

The relationship between changes in the level of motor program utilization and attention demand during the learning of a motor task was examined. The primary task involved an 86-cm horizontal arm movement which subjects attempted to complete coincident with the end of a 360 degrees sweep of a clock hand. A secondary task performed with the opposite limb required a rapid button press to an auditory probe stimulus presented at various temporal locations within each trial. Control subjects performed either the primary task or the secondary task alone, while experimental subjects performed both tasks in combination. Schmidt's (1972) index of preprogramming was used to measure the level of motor program utilization, while probe reaction time reflected the attention demand of the primary task. There was a stable level of motor programming over four consecutive days of practice (100 trials a day), but a general decrease in attention demand. Implications for an expansion of the concept of the motor program were discussed.

A Neo-Piagetian Investigation of the Serial Position Effect in Children’s Motor Learning

Children's serial motor skill acquisition was studied within a neo-Piagetian framework. High and low M-processors performed on a curvilinear repositioning task. A primacy-recency effect was evidenced for both groups on the age-related task, while a recency effect occurred for only the high M-processors on the task one stage beyond the developmental processing capacity of the subjects. High M-processors were more accurate and less variable than low M-processors. Although low M-processors performed better on the more complex task than on the simpler one, their performance never exceeded that of the high M-processors. Implications of these results for future research were discussed.

Retention Characteristics of Movement Rate Information

The retention characteristics of fast and slow movements were investigated in two experiments. Experiment 1 examined the reproduction of either fast or slow preselected movement rates after 0-sec rest, 15-sec rest or a 15-sec filled delay. Both fast and slow movement rates were rehearsable. Experiment 2 examined reproduction accuracy after subjects were required to perform a competing secondary task during the production of fast and slow movements. Although the secondary task degraded the reproduction of slow movements, it had no apparent effect upon the reproduction of fast movements. These results were interpreted as indicating partial support for Jones' (1974) notion of central monitoring of efference, and suggested that the contribution of proprioceptive feedback to movement control varies as a function of movement rate.

The Role of Verbal Estimates of Movement Error in Ballistic Skill Acquisition

The role of verbal estimates of movement error in a ballistic movement task was investigated. Two groups performed a rapid linear movement timing task for 50 trials with KR followed by 50 trials without KR. Group I was required to give a verbal estimate of movement time immediately after the task, while Group II was not. Verbal labeling of movement error did not augment performance when KR was present. When KR was withdrawn, however, Group I maintained performance, but Group II's response accuracy declined. Implications for current motor learning theories are discussed.

Evidence for Recognition and Recall Schemata

Two experiments manipulated elements postulated to be crucial for the formation of recognition and recall schemata for discrete motor skills. Experiment 1 tested predictions for the formation of a schema to recognize novel and practiced positioning movements. Sensations of practiced locations, followed by knowledge of results, enabled accurate judgment of movement extent. The specification of distances before active practice movements did not help recognition performance. To test recall schema, Experiment 2 allowed practice with active movements over specified distances, or unspecified passive movements. The allowance of response specifications during practice provided clear superiority of recall-dependent performance. This aspect of recall memory should enable the construction of movements with extents and velocities different from those practiced.

Recognition and Recall in Slow Movements

If slow positioning movements are governed only by a recognition process (e.g., Schmidt, 1975) then subject's performance should be independent of the mode or response (active versus passive). Two groups learned a criterion movement under either active or passive conditions following which KR was withdrawn. Although no differences were apparent on acquisition trials, active-group performance deteriorated dramatically during KR withdrawal while passive-group performance remained stable. These results suggest that recall and recognition are potentially separable in slow movements on the basis of the information available to the performer.

Intrinsic Feedback, Interpolation, and the Closed-Loop Theory

The amount of experience of a target location, or its surrounding locations, was manipulated to test Adams' (1971) prediction that the perceptual trace (stored perception of the correct response) is based on repeated sensations of the correct response. Sixteen learning trials, each followed by knowledge of results, on a linear-positioning task were permitted for all subjects. Each learning trial required movement to an adjustable physical stop. In learning condition without target experience, movements never terminated in a zone within which the target was interpolated. Other groups experienced movements terminating at the target point. The strength of the perceptual trace was inferred from the ability to move to the target during 20 test trials with the stop removed and without knowledge of the results. Slow movements could be made to a novel location equally as well as to a repeatedly practiced location.

The Effect of Visual Guidance on the Acquisition of a Simple Motor Task

Subjects were required to learn to depress a bar using concurrent visual feedback, which was removed for test. The overshooting found in test is attributed to visual dominance of the feedback traces; the way in which it occurs is not clear, since the reduction of the ratio of movement to display gain from 1:15 to 1:7.5 did not reduce overshooting. Performance improved after extended practice, but the direction of error remained positive. The results are discussed in terms of motor programming and feedback control of movement and are interpreted as evidence against Adams' (1971) two-trace theory.

Efference and the conscious perception of movement

Evidence was sought implicating efference in the conscious perception of movement by having subjects (n = 10) scale the time course of an active (efference present) and passive (efference absent) thumb movement Efference would presumably lead slightly in time the proprioceptive feedback from a movement and therefore cause active movements to be judged as occurring earlier than passive movements. A probe stimulus (10-msec light flash) was interjected at various temporal locations during an auditorily cued thumb movement made under the two conditions. Subjects estimated the temporal location of the flash relative to the occurrence of the thumb movement. Active movements were estimated to occur on the average 43 msec earlier than passive movements (p<.005), suggesting that efference contributed to the conscious perception of the movement.

Use of distance and location in short-term motor memory

A retroactive interference paradigm was used to determine whether kinesthetic distance, location, or distance and location cues are used at recall of a blind, simple linear movement. Students performed interpolated movements which varied distance and location cues separately or jointly. Relative to a rest condition, joint distance and location interpolation produced significant interference while no significant interference was found for interpolation of individual distance or location. The results were interpreted as supporting the involvement of multiple kinesthetic cues in the establishment of memorial representations of motor movements.

Development of a mechanism for detection of error and retention of a graded motor response

Several methods for developing an internal mechanism for error detection were compared to determine the extent to which a self-paced response could be acquired and retained without knowledge of results. During training, blindfolded subjects attempted to learn a positioning response under one of three conditions. One group was presented with the criterion end location by means of a stop and then required to recall the location with the stop removed. A second group moved the total distance of the track and then was instructed to replace the slide in a location representing a specific fraction of the total. A final group of subjects learned the criterion location by using post-response knowledge of results administered on each trial. Following acquisition subjects were give retention trials involving only repetition of the acquired response. The development of a strong mechanism for error detection was indicated only for those groups presented with the standard or with post-response knowledge of results. During retention trials (without knowledge of results), performance of the group required to learn the criterion by estimating a fraction of the total range was characterized by significanlty greater response biasing and less consistency than the other conditions. The findings were discussed in terms of several predictions from Adams' (1971) closed-loop theory of motor learning.

Relationship of objective score, perceptual trace, and practice method in learning to balance

The relationship of the perceptual trace to the objective score (raw score) under three practice conditions was the main concern of this study. Three groups of 14 Ss performed 35 trials on a stabilometer balancing task. Ss were asked to estimate how well they did after each trial. The difference between S's actual score and his guess was used as a measure of the perceptual trace. While performance and time estimations improved with practice, they correlated very low. The results were discussed in the context of Adams' closed-loop theory and gave mixed support for the theory.